Cliffs and coasts Flashcards
Overtime what causes cliffs to retreat?
weathering and erosion
What direction is the swash in longshore drift
It is in a diagonal line towards the prevailing wind
What direction is the backwash?
at a right angle to the beach, perpendicular to the swash and it is pulled back due to gravity
what is a constructive wave?
a wave with a strong swash, a weak backwash, it created a wide gently sloping beach, low in height and are less steep
what is a destructive wave?
has a weak swash and a strong backwash, breaks more frequently compared to constructive waves, more material is being removed than placed, tall and toppling, create a steep and narrow beach
what does the wave energy depend on?
the fetch
what is in situ?
in place
what is an example of something that is in situ?
weathering
What are the types of weathering?
biological
freeze - thaw
chemical
what are bedding planes?
they are horizontal joints with weaknesses which can be exposed by waves or weathering which could cause rock falls
what are vertical joints?
vertical which can cause whole sections of the cliff to fall of
why are some bedding planes less likely to collapse?
because they are tilted away
what are the ways cliffs fall?
slumping
falling
sliding
What happens when a cliff slides?
a whole column of material moves in one and will go without warning, it usually happens in vertical joints
what happens when rock falls on a cliff?
when freeze - thaw weathering makes the gaps in the rocks unstable and they get taken down by gravity it can only happen on a hard rock cliff
what happens when cliffs slump?
when a permeable rock is bellow an impermeable rock, if it becomes water logged it will slump in a curved movement it only happens in soft rock cliffs
what does hydraulic action cause?
cavitation
what coastline do headlands and bays form?
discordant coastline
How are headlands and bays formed?
when there are strips of hard and soft rock on a discordant coastline, the soft rock erodes faster creating a bay and headlands form when the hard rock is barely eroded.
what is a discordant coastline?
this is where the coastline is made up of bands of hard rock and soft rock, they are usually at right angles to the coastline
what is a concordant coastline?
where the coastline is made up of a continious line of rock parallel to the coastline
what happens when waves approach a disconcordant coastline?
the energy is concentrated on the harder rock, headlands, so there is more erosion creating caves, cracks, stacks, arches and stumps
How does a cave form
when a weakness is exposed in the headland and gets eroded by the waves
what is an example of an arch?
durdle door
how is an arch formed?
when rock is eroded by hydraulic action, abrasion and freeze - thaw weathering
how is a stack formed?
when the rock can no longer support its weight due to freeze - thaw weathering, it collapses
when is a stump formed?
when a stack is eroded and weathered over time
what is an example of a stack
old harry rocks
where are wave cut platforms found?
at the base of the headland
how is a wave cut platform formed?
rocks are hurled at the base of a cliff creating a wave cut notch
the top of the cliff will become unstable which means that the overhang will collapse into the sea providing more material for abrasion and attrition
the cliff retreats which leaves behind a rock platform - a wave cut platform - that is exposed in low tides
how is a rock pool formed?
when a boulder lodges in a depression in the rock of a wave cut platform and grinds a hollow as it rolls around in the waves after some time the depression becomes dep enough to hold water during low tide